The microprocessor controlled ground system monitor of the present invention is preferably utilized to monitor the grounding system in a telephone switching office. In the past, telephone switching offices utilized electro-mechanical switching devices to couple communication lines to permit telephone communication between parties. In such a switching system contacts are physically made or broken.
Modern day telephone switching offices have shifted from electro-mechanical switching techniques to computerized switching. In computerized switching, no electro-mechanical moving parts are utilized, but rather control signals operate to trigger electronic switching.
One of the few advantages of a telephone switching office employing electro-mechanical switches and vacuum tube amplifiers is that such components are far less susceptible to damage due to current surges caused by, for example, electrical storms than their modern day counterparts. Modern day integrated circuit devices can't withstand voltage increases or current surges comparable to their predecessors.
Accordingly, it is particularly important for modern day telephone switching offices to include a failsafe grounding system which protects the valuable equipment in the telephone switching office and which likewise enhances the probability that the telephone switching office will remain operable even after being exposed to high voltage and current surges. With such a grounding system, if a current surge is transmitted to a telephone switching office, present single point grounding practices operate to couple the current on the ground conductors to a master ground bar in the telephone switching office. Thus, if a current surge is induced on a shielded bundle of wires by, for example, lightning or inadvertent contact with a high voltage line, the high voltage will be coupled to an earth ground. In this fashion, both personnel and equipment in the telephone switching offices are protected.
In addition to avoiding damage to valuable equipment such as, for example, the digital switching system in a telephone office, telephone service interruptions are also prevented by such a grounding system. Since the provision of telephone communications is the primary source of revenue for telephone companies, any disruption in service is extremely costly to such companies.
The computer controlled switching equipment in a telephone switching office includes isolated grounds. In this regard, although other pieces of telephone switching equipment are tied into the computer electrically, each piece of equipment includes its own ground. With all the equipment separately grounded, if there is a voltage rise, the voltage rise will be reflected equally such that there will not be a potential difference between pieces of equipment. In such circumstances, if a telephone switching office staff member touches two pieces of equipment, no injury will occur if both pieces of equipment are referenced to earth ground.
Unfortunately, as many telephone switching offices have expanded to include more equipment to enhance their communication capabilities, such equipment has been installed without isolating or properly grounding the new equipment. Such faulty installation of equipment has created a serious problem in many telephone switching offices throughout the country.
In the past, telephone switching office grounding systems have been monitored often by portable monitoring units used for troubleshooting and fault diagnosis. Such prior art monitoring systems, however, provided only a limited amount of diagnostic information.
For example, in the prior art, if a high voltage or current surge enters into a telephone switching office, all the switching office has heretofore been informed of is that a current surge caused damage to a particular piece of equipment. The switching office is not informed, for example, as to the origin of the current surge, i.e., which ground conductor the current surge came in on.
In accordance with the present invention, the telephone switching company can identify that the current surge came into the telephone switching office on a particular current conductor. The telephone office can then determine, for example, that although the current surge should have been coupled to ground some of the current surge was coupled to the frame of a particular telephone office equipment. With such data the telephone switching company can identify a faulty design in the grounding system and make appropriate modifications in order to prevent such damage from reoccurring. Thus, a telephone switching office is provided with instant notice that, for example, an outside contractor installed equipment that violates accepted grounding practices. This enables timely correction to prevent costly repairs to sensitive equipment and to prevent injury to personnel.
In accordance with the present invention, sensors associated with each of the ground conductors are periodically scanned so that the current on each of the ground conductors are continuously monitored. The present system utilizes a real time clock to generate time and date information to monitor and report data regarding the ground conductors over time.
The present invention may be utilized in conjunction with single point grounding systems used in telephone switching offices where all the ground conductors are coupled to a master ground bar. This master ground bar is the single reference point for the switching offices' positive voltage and for earth ground. The present invention monitors both the AC and DC current on the ground conductors at the master ground bar.
In accordance with the present invention, the microprocessor controlled ground system monitor when it is initially set up operates to generate alarm reports on a nearly continuous basis. From the initial reports, the current flow on all conductors is determined. From this data, it can be determined what current values are normal for that particular office. Such values are then utilized to select the user's preset alarm triggering parameters. Thus, values for parameters can be empirically determined so that alarm reports are not constantly generated. Such parameters, of course, should not be set to avoid the generation of reports under circumstances where corrective action is necessary.
The present invention permits the continuous monitoring of a large number of ground conductors while reading low current values from such ground conductors. In this regard, the current flowing through the conductor generates an electromagnetic field which induces current flow in the Hall effect transducer. The current flowing in each Hall effect transducer is sensed by a Hall effect sensor which generates a voltage indicative of the current flow (which is proportional to the Hall effect sensor current). These signals are amplified and coupled to a microprocessor which converts the detected voltage levels to current levels indicative of the current flowing through the associated ground conductor.
The present microprocessor controlled grounding system is permanently installed in, for example, a telephone switching office. The present invention operates to scan a large number of ground conductors at the master ground bar by using amplified Hall effect sensors to monitor AC and DC current on the conductors. If a surge enters the telephone switching office, the surge is coupled to ground.
The present invention monitors these ground conductors to insure that the ground system is operating properly. The microprocessor continuously insures that readings are taken of the current on each of the ground conductors. The microprocessor compares the current readings with preset parameters. If a reading exceeds the predetermined parameter threshold, an alarm report is generated.
The report lists not only the current on the conductor which was the source of the surge, but also shows any current increase on the other ground conductors that are monitored. Thus, if the surge comes in on one of the ground conductors and goes out on other ground conductors and into the office equipment, the present system will indicate such and generate an alarm report to permit detection and correction of any problems.
With such a report, a non-isolated ground conductor that is coupled to the master ground bar and to the frame of a particular piece of equipment may be carefully monitored. While such a conductor should have extremely little, if any, current on it, if such a conductor, for example, exhibits an increase in current by a factor of 10 or 100, the present invention provides time and date data to correlate the increase in the current on the ground conductor with some other event, e.g., the improper installation of a piece of equipment, an electrical storm, etc.
Under certain circumstances, this excess current on a ground conductor may lead to serious damage to the computer switching equipment if, for example, it is coupled with a high voltage surge. By virtue of the present invention, such damage can be avoided.
The present invention recognizes that relatively low level surge activity over a period of time may trigger enough error messages on the telephone switching company's computer to cause an interruption in service. In this regard, such error messages generated by such relatively low voltage surges may exceed authorized memory capacity thereby operating to temporarily disable the telephone switching office computer. By virtue of the monitoring accomplished by the present invention, such relatively low voltage surges may be coupled to earth ground without raising an error message at the telephone switching office. The present invention operates to monitor such relatively low voltage surges coming into a telephone switching office so that the telephone company can identify potential problems associated therewith.
The present invention allows for the generation of reports on a local teletype, display or printing terminal. Additionally, the present invention may be used in conjunction with a modem to automatically dial a central site telephone number to convey alarm status reports thereto. The modem may also be utilized to receive telephone calls from the central site to trigger the generation of a ground system status report on demand. Other changes may be made remotely in accordance with the present invention, such as to change parameters that are being monitored or adjust the real time clock (e.g., to reflect a change to day light savings time).